This invention relates to a door-closer, more particularly to a pneumatic door-closer which can perform door closing function regardless of whether the left or the right side of the door is hinged to a door frame.
U.S. Pat. No. 4,817,238 discloses an invention of mine relating to a pneumatic door-closer in which a piston body is retained on a piston rod by means of a C-shaped retaining ring. However, in use, the retaining ring still has the possibility of loosening from the piston rod. Furthermore, compressed air can flow through the axial and radial passages of the piston body in opposite directions causing stress to concentrate on the walls defining these passages. This stress concentration reduces the lifetime of the piston body. In addition to the arrangement of the retaining ring and the passages, the improvement of this invention is also directed to a conventional door-closer which is applicable only to either of the doors 100, 200 shown in FIG. 1, but not to both of them. From an economical standpoint, it is desirable to provided with a door-closer that is applicable to both of the doors 100, 200.